RE: VIA6522 bugs details

From: Baltissen, GJPAA (Ruud) <>
Date: Wed, 9 Jul 2014 06:30:53 +0000
Message-ID: <>
Hallo Olaf,

> This doesn't seem to explain why the STOP key has no effect,

The handling of the keyboard is an interrupt driven operation. If the timer is not set or read right, there is no interrupt, thus no handling of the STOP key. Just MHO.

> If so, it is not a VIA bug but a PET software bug.

Then why don't the VIC-20 and 1540 use the serial register for transferring data? IMHO that was the idea but it had to be changed because of the "bug". Both the VIC-20 and the 1540 have two 6522s on board. While one 6522 of the two is busy with transferring data, the timer of the other 6522 can be used for generating the interrupts. Seems an obvious solution to me. But it isn't done in this way. This means that I'm either a genius for popping up this idea of how to use the two 6522s or we overlook something. And I'm afraid, if not quite sure, it is the second reason. 

With kind regards / met vriendelijke groet, Ruud Baltissen

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Received on 2014-07-09 07:00:02

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